KR101564744B1 - Boron-bearing burnable absorber nuclear fuel pellet and the method for manufacturing thereof - Google Patents

Abstract

The present invention relates to a boron-containing combustible absorbing fuel sintered body and a method of manufacturing the same, and more particularly, to a boron-containing combustible absorbing fuel sintered body containing uranium oxide powder; A boron compound as a neutron absorbing material; And a silicon compound and a titanium compound as a sintering additive, wherein the boron compound is homogeneously dispersed.
The present invention can perform sintering in a hydrogen atmosphere at a lower temperature by using a silicon compound such as silicon dioxide and titanium dioxide together with a soda-lime additive as a sintering additive, thereby sufficiently densifying UO ₂ at a temperature at which the volatilization of boron is not remarkable Vaporization of the boron is minimized by reducing the pore opening. In addition, the sintering additive of silicon compound-titanium compound can have high density and large crystal grain simultaneously because it has an excellent effect of promoting grain growth while increasing density of boron-containing sintered body at a relatively low temperature. Accordingly, the performance of the nuclear fuel can be improved because the fission gas discharge is reduced and the stress applied to the fuel rod can be mitigated by satisfying the density of 94% TD or more and the grain size of 5 탆 or more at the same time as the conventional commercial UO ₂ sintered specimen standard.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a boron-containing flame-retardant absorbing nuclear fuel sintered body and a method for manufacturing the same.

More particularly, the present invention relates to a boron-containing combustible absorbent nuclear fuel sintered body comprising a boron compound as a neutron absorbing material and comprising a sintering additive composed of a silicon compound and a titanium compound, And a manufacturing method thereof.

Nuclear power generation utilizes the heat generated by nuclear fission of uranium. Uranium oxide (UO ₂ ) sintered body is usually used as fuel for nuclear power generation.

The uranium oxide (UO ₂ ) sintered body can be produced by sintering a green pellet obtained by compression molding of uranium oxide powder at a temperature of about 1700 to 1800 ° C for 2 to 8 hours in a hydrogen gas atmosphere, A uranium oxide (UO ₂ ) sintered body having a density of 95% TD (theoretical density) and a grain size of about 6-12 μm can be produced.

The density and grain size of conventional commercial uranium oxide (UO ₂ ) sintered bodies are 94 ~ 96.5% TD and the grain size is more than 5 ㎛.

Uranium dioxide sintered body comprising 1 to 5% by weight of U ^235, U ²³⁵ As the breakdown by neutrons to generate a nuclear fission energy.

As the operation cycle of the reactor core becomes longer, the operating rate of the reactor core becomes higher, which is economically advantageous. It is advantageous to install as many fissile materials as possible in the core to increase the operation cycle of the reactor core. However, if the number of fissile materials increases, the reactivity to the main foundation becomes too high, which adversely affects the safety of the reactor core.

Therefore, in addition to the above-mentioned uranium dioxide sintered body, a combustible absorption sintered body including a combustible absorbing material having a very high neutron absorbency such as gadolinium (Gd) or erbium (Er) may be used for controlling neutrons.

Gadolinium (Gd) is the most commonly used combustible neutron absorber. However, gadolinium is one of the rare earth metals whose prices have surged recently, and it is expected that gadolinium will be required in various industrial fields, and the price will be further increased, and it is predicted that the supply and demand of gadolinium will gradually become difficult.

Accordingly, there is a demand for a method of manufacturing a flammable absorbent fuel sintered body replacing the present gadolinium.

In this combustible absorbing sintered body, a study to produce a flammable absorbing sintered body by homogeneously adding a boron (B) compound such as B ₄ C as a combustible absorbing material to uranium dioxide is disclosed in Combustion Eng. LTD., However, there is a problem that excess oxygen of uranium oxide (UO ₂ ) powder melts and reacts with boron during sintering, and B ₂ O ₃ having a low boiling point is formed and volatilized, There is a problem that the inner pressure of the fuel rod is increased due to the helium generated by burning the boron.

In order to retain the amount of boron in the sintered body so as to act as a combustible absorption sintered body after the sintering, the excessive excess boron compound should be initially added considering the volatilization amount.

However, the density of the sintered body was seriously lowered due to excessive boron volatilization and the sintered density at 90% TD or more could not be obtained even when sintered at 1600 ° C.

Kraftwerk Union Aktiengesellschaft of Germany then produced UBx (X = 2, 4, 12) and B ₄ C powders of 2 to 100 μm size each with UO ₂ powder of 15 μm size as shown in US Pat. No. 4774051 And then sintered in a reducing atmosphere and a weakly oxidizing atmosphere to prepare a sintered body in which boron is homogeneously dispersed.

UBx (X = 2, 4, 12) powders were synthesized in advance and mixed with UO ₂ powder and sintered at 1700 ℃, which is similar to the conventional sintering temperature, using a reducing atmosphere such as hydrogen gas. However, UBx powders have to be synthesized in advance, which makes it difficult to manufacture a conventional sintered body.

Further, it has been reported that boron having a sintered density of 95% TD (theoretical density) or more is homogeneously dispersed by sintering at a low temperature of 1150 ° C in a weakly oxidizing atmosphere using CO ₂ gas.

However, since the CO ₂ gas is used as the sintering atmosphere gas, there is a problem of compatibility with the existing fuel sintering process using the reducing atmosphere sintering using the hydrogen gas, and since CO ₂ gas having low diffusion is trapped in the pores of the sintered body, There is a problem that the swelling becomes serious.

Recently, Korean Patent Registration No. 1302695 discloses a method for producing a combustible absorbing nuclear fuel sintered body having a density of 90% TD or higher by adding a boron compound and manganese oxide to uranium oxide and sintering in a hydrogen gas atmosphere of 1000 to 1500 ^° C.

In this case, a combustible sintered body having a relatively high density could be produced by sintering at a low temperature using a manganese compound as a sintering accelerator, but the sintered body quality having both density and grain size at the level of the commercial UO ₂ sintered body was not achieved I did not.

U.S. Patent No. 7,139,360 and the Korean Nuclear Power Society presentation suggest a design that forms a core by increasing the number of fuel rods containing boron-containing sintered bodies instead of reducing the boron content of the sintered bodies.

This suggests that the higher the boron content of the sintered body, the higher the internal pressure of the fuel rod increases the possibility of nuclear fuel fracture. Therefore, instead of reducing the boron content, it is suggested to use a boron-containing sintered body in a large number of fuel rods (more than 50% .

In this case, much of the UO ₂ fuel rod is replaced by a boron-containing combustible absorbing fuel rod. At this time, since the boron-containing combustible absorbing sintered body is burnt under the same conditions as the conventional UO ₂ sintered body, the boron-containing combustible absorbing nuclear fuel sintered body needs to have the same performance as the conventional UO ₂ sintered body.

Accordingly, the inventors of the present invention have found that when a combustible absorption sintered body is used, when a silicon compound and a titanium compound are added to a uranium oxide containing a boron compound as a neutron absorbing material as a sintering additive, the hydrogen atmosphere sintering of a conventional uranium oxide mass- The sintered body can be sintered in a hydrogen atmosphere at a lower temperature and can exhibit a fast mass transfer rate. Thus, a combustible sintered body having both high density and large grain size has been developed and the present invention has been completed.

SUMMARY OF THE INVENTION [0006]

And a combustible absorbing nuclear fuel sintered body.

Another object of the present invention is to provide

There is provided a method of manufacturing a combustible absorbing fuel sintered body.

According to an aspect of the present invention,

Uranium oxide powder;

A boron compound as a neutron absorbing material; And

A silicon compound and a titanium compound as sintering additives,

The present invention provides a combustible absorbing nuclear fuel sintered body in which a boron compound is homogeneously dispersed.

Further, according to the present invention,

Adding a boron compound as a neutron absorbing material and a silicon compound and a titanium compound as a sintering additive to uranium oxide powder and mixing them (step 1);

A step (2) of forming a molded body by molding the mixed powder mixed in the step 1; And

Sintering the shaped body produced in step 2 in a hydrogen atmosphere (step 3); The present invention provides a method for manufacturing a combustible absorbing nuclear fuel sintered body.

The combustible absorbing fuel sintered body according to the present invention can be sintered in a hydrogen atmosphere at a temperature lower than that of the hydrogen atmosphere sintering process of the existing mass production process of a UO ₂ fueled sintered body by using a silicon compound such as silicon dioxide and titanium dioxide together with a titanium compound as a sintering additive At the temperature where the volatilization of the boron is not significant, the UO ₂ is sufficiently densified to reduce the open pore, so that the volatilization of the boron is minimized. In addition, the sintering additive of silicon compound-titanium compound can have high density and large crystal grain simultaneously because it has an excellent effect of promoting grain growth while increasing density of boron-containing sintered body at a relatively low temperature.

Furthermore, since boron compounds that have been mass produced in the past can be used, such as boron nitride (BN), boron carbide (B ₄ C), titanium diboride (TiB ₂ ), zirconium diboride (ZrB ₂ ) There is an advantage that no process is required.

The combustible absorbing fuel sintered body can simultaneously satisfy the density of 94% TD or more and the grain size of 5 탆 or more, which are standard specifications of conventional commercially available UO ₂ sintered bodies.

The combustible absorbing fuel sintered body having such a high density and large grain size can reduce the fission gas release during combustion and relieve the stress applied to the fuel rod, thereby improving the performance of the fuel.

1 is a schematic view showing an example of a method for manufacturing a combustible absorbing nuclear fuel assembly according to the present invention;
2 is a photograph of the pore structure of the combustible absorbing fuel sintered body manufactured in Example 1 by an optical microscope;
3 is a photograph of the pore structure of the combustible absorbing fuel sintered body manufactured in Comparative Example 1 by optical microscope;
4 is a photograph of the crystal grain structure of the combustible absorbing fuel sintered body manufactured in Example 1 by optical microscope;
5 is a photograph of the grain structure of the combustible absorbing fuel sintered body manufactured in Comparative Example 1, observed by an optical microscope;
FIG. 6 is a graph showing the densities of combustible absorbing nuclear fuel sintered bodies manufactured in Example 1 and Comparative Examples 1, 2 and 3; FIG.
7 is a graph showing the grain sizes of the combustible absorbing fuel sintered bodies manufactured in Example 1 and Comparative Examples 1, 2, and 3;

According to the present invention,

Uranium oxide powder;

A boron compound as a neutron absorbing material; And

A silicon compound and a titanium compound as sintering additives,

The present invention provides a combustible absorbing nuclear fuel sintered body in which a boron compound is homogeneously dispersed.

The combustible absorbing fuel sintered body can be sintered in a hydrogen atmosphere at a temperature lower than that of a hydrogen atmosphere sintering process of a conventional mass production process of a UO ₂ fuel sintering body by using a silicon compound such as silicon dioxide and titanium dioxide together with a titanium compound as a sintering additive, At a temperature where the volatilization of boron is not remarkable, UO ₂ is sufficiently densified to reduce open pores, thereby minimizing volatilization of boron.

In addition, at the sintering temperature, the flowability of the sintering additive (SiO ₂ -TiO ₂ ) is increased and the interfacial contact is improved and the mass transfer rate through the grain boundaries is rapidly increased. Therefore, The growth is promoted to have high density and large crystal grain simultaneously.

Furthermore, since boron compounds that have been mass produced in the past can be used, such as boron nitride (BN), boron carbide (B ₄ C), titanium diboride (TiB ₂ ), zirconium diboride (ZrB ₂ ) There is an advantage that no process is required.

The density of the combustible absorbing fuel sintered body may be greater than or equal to 94% theoretical density, the grain size of the combustible absorbing nuclear fuel sintered body may be greater than or equal to 5 탆, and a density of 94% It is possible to have a crystal grain size of 5 mu m or more at the same time.

The combustible absorbing fuel sintered body having such a high density and large grain size can reduce the fission gas release during combustion and relieve the stress applied to the fuel rod, thereby improving the performance of the fuel.

At this time, the boron compound may be added and mixed in an amount of 20 to 20,000 ppm by weight based on the uranium oxide.

If the boron compound is added in an amount of less than 20 ppm by weight based on the uranium oxide powder, it is difficult to exhibit neutron absorbing ability by boron. When the boron compound is added in an amount exceeding 20,000 ppm by weight relative to the uranium oxide powder There is a problem that the increase in the internal pressure of the sintered body due to the swelling of the sintered body during combustion can reach a serious level.

In addition, the silicon compound and the titanium compound may be added and mixed in an amount of 30 to 8,000 ppm by weight based on the uranium oxide.

If the sintering additive of the silicon compound-titanium compound is added in an amount of less than 30 ppm by weight based on the uranium oxide powder, the effect of promoting sintering due to the addition of the silicon compound-titanium compound is not exhibited. -Titanium compound is added in an amount exceeding 8,000 ppm by weight based on the uranium oxide powder is not economical because the uranium amount per unit volume of the nuclear fuel sintered body is relatively reduced.

The ratio of the silicon compound and the titanium compound may be added and mixed in the range of 0.14 to 20.0 based on the weight ratio of titanium (Ti) and silicon (Si) elements (Ti / Si), and the silicon compound used as the sintering additive and the titanium compound Was selected using the SiO ₂ -TiO ₂ phase diagram.

In order to obtain a sintered body having a high density and a large grain size, the sintering additive must be melted at a temperature of 1700 ° C. or lower, which is lower than the sintering temperature, and the fluidity is increased by the addition of the sintering additive, and the densification of the sintered body is promoted And grain growth must occur rapidly.

Therefore, in the case of the above composition, a combustible sintered body having a high density and a large crystal grain can be obtained.

Further, according to the present invention,

Adding a boron compound as a neutron absorbing material and a silicon compound and a titanium compound as a sintering additive to uranium oxide powder and mixing them (step 1);

A step (2) of forming a molded body by molding the mixed powder mixed in the step 1; And

Sintering the shaped body produced in step 2 in a hydrogen atmosphere (step 3); The present invention provides a method for manufacturing a combustible absorbing nuclear fuel sintered body.

Here, an example of a method of manufacturing the combustible SAR fuel pellets according to the present invention is schematically shown in FIG. 1,

Hereinafter, a method of manufacturing the combustible SAR fuel assembly according to the present invention will be described in detail.

In the method for producing a combustible absorbing fuel sintered body according to the present invention, step 1 is a step of adding a boron compound as a neutron absorbing material and a silicon compound and a titanium compound as a sintering additive to uranium oxide powder and mixing them.

Conventionally, as a method of producing a combustible absorption sintered body, a boron compound is used as a neutron absorbing material. However, during the sintering, surplus oxygen of the uranium dioxide powder reacts with boron to dissolve, and B ₂ O ₃ having a low boiling point is formed, There is a problem that the inner pressure of the fuel rod is increased due to the helium generated by the combustion.

In addition, in order to retain a certain amount of boron in the sintered body, an excessive amount of excess boron compound had to be initially added. However, as the excess boron volatilized, the density of the sintered body became seriously low and sintered at a high temperature of 1600 ° C, The sintered density can not be obtained.

However, in the present invention, since sintering can be performed at a low temperature by adding a silicon compound and a titanium compound as additives for sintering, uranium dioxide is sufficiently densified at a temperature at which volatilization of boron is not remarkable, Can be minimized.

Further, the sintering additive of silicon compound and titanium compound is excellent in enhancing the density of the boron-containing sintered body and promoting the grain growth at a relatively low temperature, and can produce a sintered body having a density of 94% TD or more and crystal grains of 5 탆 or more.

Furthermore, such flammable sorption fuel sintered bodies improve the performance of the nuclear fuel because the emission of fission gas during combustion is reduced and the stress applied to the fuel rod can be mitigated.

Step 1 of the present invention is a step of producing a raw material powder by adding a boron compound as a neutron absorbing material and a silicon compound and a titanium compound as a sintering additive to uranium oxide powder and mixing them.

The boron compound of step 1 may be at least one compound selected from the group consisting of boron nitride (BN), boron carbide (B ₄ C), titanium diboride (TiB ₂ ) and zirconium diboride (ZrB ₂ ) , But boron nitride can be used. However, the boron compound is not limited thereto. Any boron compound capable of forming B ₂ O ₃ by reacting with surplus oxygen of UO ₂ during sintering can be suitably selected and used have.

At this time, the boron compound of the step 1 may be added and mixed in an amount of 20 to 20,000 ppm by weight based on the uranium oxide powder.

If the boron compound is added in an amount of less than 20 ppm by weight based on the uranium oxide powder, it is difficult to exhibit neutron absorbing ability by boron. When the boron compound is added in an amount exceeding 20,000 ppm by weight relative to the uranium oxide powder There is a problem that the increase in the internal pressure of the sintered body due to the swelling of the sintered body during combustion can reach a serious level.

The silicon compound of step 1 may be at least one compound selected from the group consisting of silicon, silicon oxide, silicon nitride, silicon carbide, silicon chloride and silicon sulfide, but the silicon compound is not limited thereto, Silicon dioxide (SiO ₂ ) can be used.

The titanium compound of step 1 may be at least one compound selected from the group consisting of titanium, titanium oxide, titanium nitride, titanium carbide, titanium sulfide, titanium chloride, and titanium fluoride. However, the titanium compound is not limited thereto, It can be preferably used titanium dioxide (TiO _2).

At this time, the silicon compound and the titanium compound of the step 1 may be added and mixed in an amount of 30 to 8,000 ppm by weight based on the uranium oxide powder.

If the sintering additive of the silicon compound-titanium compound is added in an amount of less than 30 ppm by weight based on the uranium oxide powder, the effect of promoting sintering due to the addition of the silicon compound-titanium compound is not exhibited. -Titanium compound is added in an amount exceeding 8,000 ppm by weight based on the uranium oxide powder is not economical because the uranium amount per unit volume of the nuclear fuel sintered body is relatively reduced.

The ratio of the silicon compound and the titanium compound in the step 1 may be added and mixed in the range of 0.14 to 20.0 based on the weight ratio (Ti / Si) of the titanium (Ti) and silicon (Si) The composition of the silicon compound and the titanium compound was selected using the SiO ₂ -TiO ₂ phase diagram.

In order to obtain a sintered body having a high density and a large grain size, the sintering additive must be melted at a temperature lower than 1700 ^o C below the sintering temperature. The addition of the sintering additive increases the fluidity and the contact with the uranium oxide interface, Accelerated and grain growth must occur rapidly.

Therefore, in the case of the above composition, a combustible sintered body having a high density and a large crystal grain can be obtained.

In step 1 of the present invention, a silicon compound and a titanium compound are added as a sintering additive. For example, a silicon compound and a titanium compound are heat-treated at 1000 ^° C to 1600 ^° C to synthesize the powder. can do.

As described above, the silicon compound and the titanium compound are heat-treated together at 1000 ^° C to 1600 ^° C to synthesize a silicon compound and a titanium compound, and the powder produced by pulverizing the above substance is similar to a mixture of the silicon compound and the titanium compound It has sintering promoting effect.

In the method of manufacturing the flammable SAR resin according to the present invention, the step 2 is a step of molding the mixed powder mixed in the step 1 to produce a molded article.

The method of manufacturing the molded article of step 2 may be manufactured by, for example, molding the mixed powder prepared in step 1 at a molding pressure of 2 to 6 ton / cm ² into a molding mold, The production method is not limited thereto, and a method known to those skilled in the art can be appropriately selected and used.

At this time, the molded body manufactured in the step 2 may have a boron compound as a neutron absorbing material and a silicon compound and a titanium compound as a sintering additive agent uniformly dispersed.

In the method for manufacturing the combustible absorbing fuel sintered body according to the present invention, step 3 is a step of sintering the shaped body produced in step 2 in a hydrogen atmosphere.

Conventionally, in a method for producing a uranium oxide sintered body, a compact obtained by compression-molding uranium oxide powder is sintered in a hydrogen gas atmosphere at a temperature of about 1700 to 1800 ° C for 2 to 8 hours. However, The excess boron compound was added at an early stage, so that the density of the sintered body was seriously lowered due to excessive volatilization of the boron. As a result, the sintered body could not have a sintered density higher than 90% TD even when sintered at such a high temperature.

However, in the present invention, since sintering can be performed at a low temperature by adding a silicon compound and a titanium compound as sintering additives, even when the volatility of boron is not remarkable, uranium dioxide is sufficiently densified to reduce open pores, Can be minimized. Furthermore, the sintered body produced by the above method has a density of 94% TD or more and a crystal grain size of 5 탆 or more, which satisfies the specification of the commercial sintered body.

The hydrogen atmosphere in step 3 may be a hydrogen-containing gas atmosphere further including at least one selected from the group consisting of argon, nitrogen, carbon dioxide, and water vapor, but the hydrogen-containing gas atmosphere is not limited thereto.

On the other hand, the sintering of step 3 can be performed at a temperature of 1450 to 1700 ° C.

If the sintering in step 3 is performed at a temperature lower than 1450 ° C, the density of the sintered body is lowered. If the sintering in step 3 is performed at a temperature higher than 1700 ° C, The density of the sintered body to be manufactured may be lowered.

Hereinafter, the present invention will be described in detail with reference to Examples. However, the following examples are illustrative of the present invention, and the present invention is not limited by the following examples.

≪ Example 1 >

Step 1: Powder of uranium oxide (UO ₂ ) was mixed with boron nitride as a neutron absorbing material, and silicon dioxide and titanium dioxide were added together as a sintering additive.

At this time, the boron nitride was added in an amount of 4,000 ppm by weight based on the uranium oxide powder, and the silicon dioxide-titanium dioxide was added in an amount of 3,000 ppm by weight based on the uranium oxide powder. The weight ratio of silicon dioxide to titanium dioxide added was 53% and 47%, respectively.

Step 2: In step 1, the mixed powder was pressurized by applying a pressure of 3 ton / cm < 2 >

Step 3: The molded body produced in the step 2 was sintered in a hydrogen atmosphere at 1560 캜 for 2 hours to prepare a combustible sintered body.

 ≪ Comparative Example 1 &

A combustible sintered body was produced in the same manner as in Example 1, except that the mixed powder was prepared without adding the sintering additive in the step 1 of Example 1 above.

≪ Comparative Example 2 &

The sintered combustible absorbing nuclear fuel sintered body was manufactured in the same manner as in Example 1, except that 3,000 wt. Ppm of silicon dioxide was added to the uranium oxide powder alone as the sintering additive in Step 1 of Example 1 to prepare a mixed powder. Respectively.

≪ Comparative Example 3 &

The procedure of Example 1 was repeated except that titanium dioxide was added as a sintering additive in an amount of 3,000 ppm by weight based on the uranium oxide powder to produce a mixed powder in Step 1 of Example 1 to prepare a combustible absorbent nuclear fuel sintered body Respectively.

≪ Comparative Example 4 &

The procedure of Example 1 was repeated except that titanium dioxide was added as a sintering additive in an amount of 30 ppm by weight based on uranium oxide powder alone to produce a mixed powder, thereby preparing a combustible absorbent nuclear fuel sintered body Respectively.

EXPERIMENTAL EXAMPLE 1 Analysis of Sintered Density of Flammable Absorption Fuel Sintered Body

Sintered densities of the combustible absorbent nuclear fuel sintered bodies produced in Example 1 and Comparative Examples 1, 2, 3 and 4 according to the present invention were analyzed using the immersion method. The results are shown in Tables 1 and 6 Respectively.

Amount of BN added
(ppm) Additive composition Of sintering additive
Addition amount Sintered density
(% TD) Grain size
(탆) Example 1 4000 SiO ₂ -TiO ₂ 3000 96.0 19.6 Comparative Example 1 4000 No additive 0 93.8 3.6 Comparative Example 2 4000 SiO ₂ 3000 93.2 3.1 Comparative Example 3 4000 TiO ₂ 3000 93.5 3.5 Comparative Example 4 4000 SiO ₂ -TiO ₂ 30 93.7 3.7

As shown in Table 1 and FIG. 6, it can be seen that the sintered body manufactured according to Example 1 exhibits significantly higher sintered density than 2% TD as compared with the sintered body prepared by adding only the boron compound without the sintering additive of Comparative Example 1 have.

In addition, the sintered body manufactured in accordance with Example 1 had a sintered body added with silicon dioxide alone as the sintering additive of Comparative Example 2 and a sintered body of 2% as compared with the sintered body added with titanium dioxide alone as the sintering additive of Comparative Example 3, TD < / RTI >

It can be seen that the sintered body prepared according to Example 1 satisfies the conventional commercial UO ₂ sintered body density standard of 94 to 96.5% TD.

Thus, it can be seen that a high sintered density can be obtained by adding the silicon compound and the titanium compound together as the boron compound and the sintering additive in the method of manufacturing the combustible sorption fueled sintered body according to the present invention.

<Experimental Example 2> Microstructure analysis of combustible absorbing fuel sintered body

The surfaces of the sintered combustible fuel sintered body manufactured in Example 1 and the sintered body prepared in Comparative Example 1 were observed using an optical microscope. The results are shown in FIGS. 2 and 3.

As shown in FIG. 2 and FIG. 3, it can be seen that the number of pores represented by black dots is very small as compared with the sintered body produced in Comparative Example 1, in the combustible absorbing fuel sintered body manufactured in Example 1.

This is because in the case of the sintered body manufactured in Comparative Example 1, the sintered body was not densified properly due to sintering without the sintering additive. On the other hand, in the case of the sintered body manufactured in Example 1, the densification can be performed well due to the addition of silicon dioxide-titanium dioxide, so that the number of pores is not small, and thus it can be shown that the density is high.

From the above results, it was confirmed that the sintered body exhibiting a high sintered density can be manufactured by adding the silicon compound-titanium compound together with the sintering additive in the method of manufacturing the combustible absorption sintered body according to the present invention.

<Experimental Example 3> Grain size analysis of combustible absorbing fuel sintered body

The grain sizes of the combustible absorbing fuel sintered bodies manufactured in Example 1 and Comparative Examples 1, 2 and 3 according to the present invention were observed using an optical microscope and then shown in FIGS. 4 and 5, And the results are shown in Table 1 and FIG.

4 and 5 show the crystal grain structure of the sintered body produced according to Example 1 and Comparative Example 1 of the present invention. The sintered body produced according to Example 1 exhibits significantly higher grain structure than the sintered body produced according to Comparative Example 1. [

Further, as shown in Table 1 and FIG. 7, it can be seen that the sintered body manufactured according to Example 1 exhibits a grain size of 5 times or more larger than that of the sintered body produced by adding only the boron compound without the sintering additive of Comparative Example 1 have.

In addition, the sintered body produced according to Example 1 has the same effect as the sintered body prepared by addition of silicon dioxide alone as the sintering additive of Comparative Example 2 and the sintered body added with titanium dioxide alone as the sintering additive of Comparative Example 3 Which is larger than twice the grain size.

It can be seen that the sintered body manufactured according to Example 1 satisfies the standard size standard of the sintered ceramics of the conventional UO ₂ of 5 탆 or more.

Thus, it can be seen that large grains can be obtained by adding the silicon compound and the titanium compound together as the boron compound and the sintering additive in the method of manufacturing the combustible absorbing fuel sintered body according to the present invention.

Claims (17)

delete delete delete delete delete Adding a boron compound as a neutron absorbing material and a silicon compound and a titanium compound as a sintering additive to uranium oxide powder and mixing them (step 1);
A step (2) of forming a molded body by molding the mixed powder mixed in the step 1; And
Sintering the shaped body produced in step 2 in a hydrogen atmosphere at a temperature of 1450 to 1700 (step 3); Lt; / RTI &gt;
The ratio of the silicon compound and the titanium compound in the step 1 is added and mixed in the range of 0.14 to 20.0 based on the weight ratio of titanium (Ti) and silicon (Si) elements (Ti / Si) Wherein the density is at least 94% theoretical density (TD) and the grain size of the sintered body is at least 5 m.
The method according to claim 6,
The boron compound of step 1 is at least one compound selected from the group consisting of boron nitride (BN), boron carbide (B ₄ C), titanium diboride (TiB ₂ ) and zirconium diboride (ZrB ₂ ) Wherein said method comprises the steps of:
The method according to claim 6,
Wherein the boron compound of step 1 is boron nitride (BN).
The method according to claim 6,
Wherein the silicon compound of step 1 is at least one compound selected from the group consisting of silicon, silicon oxide, silicon nitride, silicon carbide, silicon chloride and silicon sulfide.
The method according to claim 6,
Wherein the titanium compound of step 1 is at least one compound selected from the group consisting of titanium, titanium oxide, titanium nitride, titanium carbide, titanium sulfide, titanium chloride and titanium fluoride.
The method according to claim 6,
Wherein the silicon compound and the titanium compound of step 1 are silicon dioxide (SiO ₂ ) and titanium dioxide (TiO ₂ ), respectively.
The method according to claim 6,
Wherein the boron compound of step 1 is added and mixed in an amount of 20 to 20,000 ppm by weight based on the uranium oxide powder.
delete The method according to claim 6,
Wherein the silicon compound and the titanium compound of the step 1 are added and mixed in an amount of 30 to 8,000 ppm by weight based on the uranium oxide powder.
The method according to claim 6,
Wherein the molded article produced in the step 2 is characterized in that a boron compound as a neutron absorbing material and a silicon compound and a titanium compound as a sintering additive are homogeneously dispersed.
delete The method according to claim 6,
Wherein the hydrogen atmosphere in step (3) is a hydrogen-containing gas atmosphere further comprising at least one selected from the group consisting of argon, nitrogen, carbon dioxide, and water vapor.

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